Barbara Liston, Reuters

An FBI agent who fired six to eight gunshots and killed a man being questioned last year about his connection to a suspect in 2013 Boston Marathon bombings has been cleared of any wrongdoing, officials said on Tuesday.

The agent's actions were justified to defend himself and a Massachusetts state police officer after the man threatened them in his Orlando apartment last May, according to separate reports issued by Florida State Attorney Jeff Ashton and the U.S. Justice Department.

"A complete review of the investigation leads me to conclude that criminal charges against the special agent of the FBI are not warranted," Ashton wrote in a letter to FBI Director James Comey.

Ashton's findings echoed the FBI's account of the shooting death of Chechen immigrant Ibragim Todashev, 27, who the agency has said suddenly attacked and injured the FBI agent during the interrogation.

Todashev was an acquaintance of Tamerlan Tsarnaev, one of two Chechen brothers accused of carrying out the April 2013 bombings at the Boston Marathon that killed three people and wounded more than 260.

At the time of his death, Todashev was being questioned about his suspected involvement in a September 2011 triple murder case in Massachusetts that law enforcement officials believed was linked to Tsarnaev.

After a long interview with law enforcement officers, Ashton said Todashev was writing a statement about his involvement in the triple murder when he suddenly threw a coffee table, striking the agent in the head and causing him to fall to the ground bleeding.

Todashev then ran to the kitchen while the agent and police officer pulled their weapons and he returned holding what they described as a pole - the metal handle of a broom stick - over his head.

The FBI agent shot Todashev three to four times as he approached the police officer, according to Ashton. Todashev dropped to his knees, then sprang toward the officer in a low-angled lunge. The agent then fired three or four shots, killing Todashev, Ashton said.

The Massachusetts police officer whom Todashev was lunging for when he was shot by the FBI agent said he had feared for his life.

"There's no question in my mind that if he had gotten a weapon from us, if it hadn't turned out the way it did, we might not be here today," the officer said.

The prosecutor said the entry angle of the bullets alleviated his concern about Todashev being shot in the back because it confirmed the account by the police officer, who had not seen the autopsy.

Ashton said there was no evidence the agent, who was aware of Todashev's training in mixed martial arts, acted with malice or committed intentional misconduct.

U.S. prosecutors also cleared the FBI agent of wrongdoing in findings released on Tuesday.

"Todashev ignored commands to show his hands, armed himself with an approximately five-foot long, hollow, metal utility pole and charged back" toward the FBI agent and police officer, a report by the Justice Department said.

But the leader of a Muslim civil liberties group said the Florida prosecutor's inquiry did not exonerate the agents "of any negligence or wrongdoing on their part which could have avoided the death of a suspect in questioning."

"The prosecutor's review was limited to a very narrow review of whether the officer was justified to use lethal force during the seconds he pulled the trigger," said Hassan Shibly, executive director of the Tampa-based branch of the Council on American-Islamic Relations (CAIR).

The FBI account of the shooting has also been questioned by Todashev's father, who said his son was unarmed.

Shibly has said his organization's independent review concluded that Todashev, who was in the United States legally, was shot seven times and received a major wound, possibly a bullet hole, to the back of the head.

The CAIR investigation also found blood splatter and other physical damage at the scene that pointed to Todashev being shot while he was lying on the ground, Shibly added.

Tamerlan Tsarnaev, 26, died on April 18, 2013, after a gunfight with police that took place several days after the April 15 bombing attack, while he and brother Dzhokhar, now 20, were trying to flee the city. The younger Tsarnaev was wounded and later arrested and is awaiting trial on charges that could result in the death penalty if he is convicted.